In the past, wristwatches having a timepiece function and a function to measure living-body data such as pulsation/blood pressure are known. Such a wristwatch has, for example, an air chamber and a cuff that fluid communicates with the air chamber within a case thereof with a pressure sensor extending into the air chamber. In this wristwatch, the air within the cuff is intermittently pressurized in accordance with pulsation of blood in the blood tubes within a user's wrist. Resulting changes in the air pressure are transmitted into the air chamber. Changes in the air pressure within the air chamber are sensed by the pressure sensor, thereby displaying the changes as blood pressure or pulsation.
The whole cuff is molded from an elastically deformable material such that after the cuff is deformed elastically by the pressure, it will be restored to its original state due to elasticity.
When the whole cuff is molded from the elastic material, however, only that part of the cuff that comes directly into contact with the user's wrist will absorb the push force given by the pulsation. Thus, the cuff would be elastically deformed locally. Therefore, a uniform change cannot be produced in the air pressure within the fluid chamber and hence high accuracy of pulsation measurement is difficult to obtain.
It is therefore an object of the present invention to provide a wrist-worn apparatus capable of sensing pulsation of blood in the blood tubes of the user's wrist with high accuracy.